This proposal deals with the characterization of endogenous benzodiazepines and benzodiazepine-like molecules. The working hypothesis is that the brain has endogenous benzodiazepines that might be used as natural anxiolytic, antiepileptic and muscle relaxing substances. Recent evidence for the existence of these substances has been obtained in several laboratories where molecules with the benzodiazepine ring structure have been purified from animal brains. The aim of this proposal is to determine whether these benzodiazepines are truly endogenous and are synthesized by the brain, or whether they are exogenous (either biosynthesized by microorganisms or plants or chemically synthesized by the pharmaceutical industry). This study might be relevant i) for environmental medicine, toxicology and nutrition, if the brain benzodiazepines had their origin either in the pharmaceutical industry or they were exogenous natural products made by microorganisms or plants and ii) for better understanding the ethiology of anxiety and some forms of epilepsy, if these or similar BZD-like substances were made by the brain and were used for the endogenous modulation of GABA neurotransmission.